This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Yilbegan (Turkic)
In a legend of the Altai, there was a seven-headed ogre, Yelbeghen, taking revenge from the Sun and the Moon, and used to eat them. The Ülgen shot arrows to Yelbeghen. This ogre sometimes chewed the stars in his mouth and broke them into pieces and then spit them out. Therefore, stars used to run away from him into the sky... According to Altai people, eclipse of the Moon used to take place because of this ogre. For this reason, when there is moon eclipse they say: ‘’Again Yelbegen (seven-headed ogre) ate the Moon...’’
Yelbeghen, sometimes Yelmogus is generally considered to be a creature separate from dragons and a polar opposite to them in its nature. It is a being of pure evil, a dragon-like beast and dreadful monster with no reason, that usually lives in dark and hostile places, or guards unreachable locations in fairy-tales.